Private automatic branch exchange system



July 29, i947, F.- P. GoHoRr-:L 2,424,563

' `PRIVATE AUTOMATIC BRNCH EXCHANGE SYSTEM 'V Filed June 22,. 1945 5 sheets-sheet 1 Fir/wm n caf/afa Filed June 22, 1945 5 shets-sheet 2` KMSSK kf 2 im NN July 29, l947 F. P. GoHoREL PRIVATE AUTOMATIC BRANCHl EXCHANGE SYSTEM Filed `fune 22. 1945 5 sheets-sheet s .sw/7 ra/supo INVENTOR Y fmm/vonaauo/ea BY ZGENT July 29, 1947. F, P, GOHQREL `2,424,563

PRIVATE 'AUTOMATIC BRA-NGE EXCHANGE SYSTEM Filed June 22,` 1943' 5 sheets-sheet 4 E 1, :le v INVENTOR I BY l l AG .uf

F. Fi. GoHoREl.

" July 29, 1947.

PRIVATE AUTOMATIC BRANCH ECHANGE SYSTEM 5 sheets-'sheet 5` Filed June 22, 1943 m ai NNvO K laieniecl .uy 29,

cm1-Eo PATENT omas I 2.424,56?, PRIVATE .inconscio sussen XCHAGE SYSTEM Fernand P. Gchdrl;Lyorifrj, 'ssif'go'r to International Standard Electric' Corporation, New York,- N. Y.; a corporatin Vof Delaware implication This invention relates to new and InL provements in private automatic brat-ic change switchboards by nieas of Vith-ioni ocal subscribers 'can be" connected vitli` cin aiitlier and also with outside telephone iiet'vvcirl.`

It is Customary to arrange specialfacilities for some or all the subscribers o`f a P.*A. rB1 X,'such as direct connections with the outside network, the transfer of an outside c'all f'ro'ril or'ie tatiiii-t another With or Without the intervention# oi `ari operator, etc.

In known systems such special services-were usually provided under selective control by la P. E. X station who had to dial a certairi nrifiber or depress numerical keys'. i

The object of the present invention is to"`Jro-' vide a P. A. B. X` in which simply by pushing a; button a P. B. X station may control th gier-V iormance of special operations, e. g. to obtain direct connection to the' outside network; to trans; fer calls from one station to another, etc;

According to one featureV of the"invention?.air'` tary switch is provided with Wipers. connecte to an outside line and has `access to the stations? of the P. A. B. X which are connected totlieterl mnal bank of the switch.

According to another feature of theV invention, the device for controlling the' svvitcliixigv of a calll from one station' to another is associated with Still another feature of the invention consistsin the" provision of means at the P. B. X operators-l position to cut in on a P. B. X connection and? to inform on'e of the parties engaged in such* connec; tionl that an outside call is avvaitingl him. 'The P. B1 X subscribers engaged' inua local conversa# tion are advised when such forced listeningllff takes place;

According to another feature of the; invention;

a relay automatic switchboard is provided with'` local junction circuits and one ormre czilrcir-`` cuits. A local connection is first established over a junction circuit and a call circuit associated with a connector. Then thecall .circuit andl t'h'e" claims. (oi-msnm connector are released and the talking onnectioii is established o er the junction circuit.` The calling and called subscribers stations are supllied with' cur-rent through a device independent fthe' connector. u

Another feature of the invention consists in the' ia'rovision of arrangements whereby When the out- 'ii lir' is I-l'titlin One of the local junction circuits disengaged and cannot be seized by a P; B. X call. This will insure immediate re# Dlyt'a'call coming from the outside network.

Another feature o'f the invention provides for the" transfer of calls from one P. B. X stationv to another through a junction circuit,` a connector eduipent and a call circuit.

Various* other characteristic features ofthe invntio will appear from the descriptions which follow ofthe embodiments of the invention illustrated` in the drawings" in which:

Figure 1 is a general' diagram of the automatic switchboard with rotary switches;

liigiirsyZ"and 3' are detailed circuit diagrams of the automatic switchboard with rotary switches;

i Figure 4 is' a general diagram oi a relay automatic switchboard; Y

Figures 5' and 6 are detailed circuit diagrams of a relay automatic switchboard; and

Figure' 7 shows the Way in which Figures' 2 to 3 arrcl'` to"'6 should be' connected.

` First of all an explanation shall be given of the gen-eral operation. of an automatic" Switchboard Withrotary switches; reference being madev to Figure l.

`Wllen a` local subscriber suchl as P1 wishes to call' another local subscriber, such as P25, h'e lifts his hand-set. I-Ie is connectedthrough a local connectionA circuitfcomprising a finder CH and a connector CG: He'receives thejdialing signal and then dials the' number of the subscriber P2. whichA results in- COf being operated to select Pzs line. If P2 is disengaged heA lifts his hanfdset and, thereby. stops the t-ransrnission` of the ringing through the circuit CHT-COL If P2 is-engaged` the busysignalis sen-t to P1..

When;- a local subscribersuch as P1' wishes to establish a call withlth'e outside network L1-L2 andlifts` his-handset,`- `l'lehvvill be connectedto a local-connecting circuit CEI-#CO as before. When he receives Athe transmission signal heipresses dOWn--abutton' associated With his stationwhich has the effect of transferring the' call toV a switch CR assof'iatedr with thefutside lie L'1-L2- This switch sput into operationtoliunt for Pis line.

3 When the line is found, CR stops and P1 is connected with L '.-La

When a call coming from the outside network is received on the line Li-Lz, an operator at 'station PS listens-in on the line. She then operates the transfer key forming part of her station,y and comes into communication with the local con-` necting circuit through the equipment ER. She calls the required station, informs him of the call, and the transfer operation then takes place, as will be indicated in what follows, the station PS being then disconnected from the equipment ER.

When a station such as P1 is in communication with the external network, and it is desired to effect an operation whereby one 'operator switches through to another operator, and the subscriber then asks that another local station such as Pz be connected and the outside line held, the operato1l presses a button at her station causing the network L1-L2 to be held and P1 to -be connected to the local connection circuit CH-CO. The subscriber P1 dials Pzs number, and the call is established. In order to obtain the outside call again P1 presses the button forming part of his station, and in ER the local call is cut off and P1 placed in communication with Li-Lz.

In order to transfer a call from the external network, the station P1, for example, rst of all switches one operator to another operator who will then be in communication with the subscriber, for example, P2, to inform him that he should take the -outside call. The subscriber P2 presses the button forming part of his station which puts the switch CR in operation and which searches for the line of the P2 station. The subscriber P1 may now replace his receiver. The local connection circuit CH-CO is released and P2 is in communication with L1--L2 through CRand ER.

A detailed explanation shall now be given with reference to Figs. 2 and 3 of the operation of this automatic switchboard having rotary switches. In the description which follows, the relay contacts which are closed when the relay is energized, are given by placing in front of the numeral designating the spring the letter T, and the contacts which are closed when the relay is de-energized by placing the letter R in front of the number.

Local caZls.-When a subscriber, such as P1, lifts his handset his line relay A is energized over the following circuit: battery, winding of A, RC1, wire of line I1, station P1, line I2, RC2 and earth. The relay A closes the following circuit for the relay II: earth, TA2, winding of relay II, bank contact of the rest position associated with the wiper L, wiper L on the rest position, R2I, resistance R1 and battery.

The relay II completes a circuit for relay 'It` earth, lower winding of I, R83, contact of the electromagnet RCO of the connector CO, contact of the electromagnet RCH of the finder CH, TI I2, resistance R1 and battery,

The energizing circuit of the electromagnet RCH is established via: battery, electromagnet RCH, TI I I, T'II, RIIJI and earth. The electromagnet RCH attracts its armature and opens the circuit of the relay 'I which at TII opens the circuit of the electromagnet RCH'causing the wipers of the finder CH to advance by one step. Whenl the armature of electromagnet RCH is released, the circuit of the relay 'I is again completed and this relay recloses the circuit of RCH, Thus the stepping of the wipers of CH is continued until they reach the bank contacts of the calling line whereupon the following circuit is closed for re- 4 lay I0: battery, windings of relay I Il in series, TI I4, wiper T of CH, bank contact t, TA1, winding of relay C and earth. The relays I0 and C become energized.

The relay I short-circuits its upper winding by TI 02 but is held on its lower winding. At RI 0I it opens the circuit of the electromagnet RCH and the wipers of CH are arrested.

The circuit of relay I is completed via: battery, upper winding of relay I, upper winding of relay 3, TI05, wiper A of CH, conductor I1, station P1,

`conductor I2, bank contact b, wiper B of CH, TI04, lower Winding of relay 3, lower winding of relay I and earth.

The relay 3 whose windings are in opposition does not attract its armature. The relay I closes the circuit of relay 2 through the non-inductive upper winding of the relay 5. The relay 2 opens at R2I the circuit of the relay II, which drops. A holding circuit for relays I0 and C is completed over T25 when the relay II becomes deenergized,

The dialing tone is sent to the calling subscriber over the following circuit: signal generator, R85, R62, R4'3, condenser Cm, TI05, wiper A and Lstation P1.

'I'he calling subscriber P1 proceeds to dial the called subscribers number. Every time the dial opens the circuit, the relay I drops and completes the following circuit for the electromagnet RCO of the connector CO: battery, electromagnet RCO, RBI, R66, RIZ, T22 and earth. The wipers of CO will thus advance step-by-step under the action of the relay I which is itself controlled by the im-pulses sent out by the dial of the station P1. As soon as the first impulse of an impulse series is received the circuit of the relay 5 will be completed by: battery, upper and lower windings of 5, T26, RII, RI5I and earth. The relay 5, whose lower winding is short-circuited when I is energized, is slow to de-energize and remains up throughout the impulse series in the same way as the relay 2.

When a series of impulses has been received, therelay 5 drops. The relay 2 continues to be held over TI I.

.The switch CO will advance by a number of steps which is equal to the number of the impulses received, and finally stops on the bank contacts of the called subscribers line.

If the called subscriber is free, the relay 8 will be energized via the following: battery, windings of relay 8, R53, R64, T23, RI43, wiper T1 of CO, bank contact t, cable 11, winding of relay C of the called station, and earth.

Ringing current is sent to the called subscriber via: the signaling device, resistance R2, R42, T86,.RI44, wiper B1 of CO, bank contact b, cable o, conductor I2 of the line of the called station, condenser and bell of the called station, conductor I1, wire a in the cable v, bank contact a of CO, wiper A1 of CO, RI45, T81, R44, relay 4 and battery. The relay 4 which is insensitive to alternating current is not energized during the transmission of the ringing current, but is energized when the called subscriber answers. When the relay 4 is energized, it is maintained via: T4I, resistance R3, T24 and earth.

The relay 'I is then energized in the following circuit: battery, upper winding of 1, upper winding' of 9, T44, T81, RI45, wiper A1 of CO, bank contact a of the called station, lines and called station, bank contact b, wiper B1 of CO, RI44, T86, T42, upper winding of 9, lower winding of I and earth. The relay 9, whose two windings in assignee '5 opposition are energized, does not attract its arma-turel The" two subscribers are now connected by' the following circuit: calling station,wiper'A of CH, TM5, condenserl Cm, T43, T86, RI44, wiper B1 of CO1, called station, wiper Ar, RI45, T81; condenser 611.2,` TIM, wiper Bv of CH and" calling station.

When the calledf subscriber replaces his handset, he opensithe-circuitoi the relay 1.. The relay I becomesde-energized when the calling subscriber replaces his handset.

The relay 2,shortecircuitediby: RIfI, RIEIl and earth;d'e.energ-izesL and atl-T25,l opens the holding circuit of relays I and Which release. At T23 the relay 2 opens the circuit of the relay 8 and at T24 the circuit of the relays 4-and 6. When the called subscriber replaces his receiver.

the relay 'I drops after 4 has dropped, its circuit` being opened at T42 and T44. The relay 1 is re-energized over its lower winding via R83, contact of the electromagnet RCO, contacts of the electromagnet RCI-l, multiple bank contacts of CO, wiper L, R2 i, resistance RI and battery. The circuit of the electromagnet ROO is thenv cornpleted via: battery, winding of RCO, RI I I, TTI, RIM and earth. The electromagnet RCO attracts its armature and by its contact opens the circuit of the relay 'I which drops again, opening the circuit of RCO, which releases its armature thus again producing the advance by one step of the wipers of CO. When the electromagnet RCO has released its armature, the circuit of the relay l is again completed and the Wipers of CO will advance by a further step. It will be seen that by the play of the relay l, and of the contact RCO, the wipers of CO will advance step-by-step up to the rest position. When the wipers reach this position, the circuit of the relay 'I is opened in the wiper L.

If the called subscriber is engaged when the wipers of CO stop on the bank contacts of the line, the following circuit of the relay 6 will be completed: earth, upper winding of 6, T52, T23, RI 43 and earth on the wiper T1 through the lower winding of the relay I5, or oi the relay 8, depending whether the called subscriber was calling or called in the conversation involved.

A busy tone is, therefore, always sent to the calling subscriber Via: signaling device, T62, R43, condenser Cm, T l 35, wiper A of CH, bank contact a, line and` station P1. When the relay v has dropped the relay 6 is held over its lower Winding Via T53, R5i and T24. When the calling subscriber replaces his handset the release takes place as previously described.

If it is desired to increase the capacity of the private automatic switchboard, two series of Wipers are provided on the connector CO, and a relay E4 is added. The first series of wipers AI, BI, TI', and TR1 are connected to the rest contacts of the relay I4, and the second series A2, B2, TR2, to the operating contacts. If the called subscriber is accessible over the first series of wipers the relay I4 remains de-energized. If, howeyer, the called subscriber must be reached over' the second series of wipers, which is indicated by the transmission of a certain rst digit, the relay I4 will be energized in the following circuit: earth, T24, upper winding of relay I4,

bank contact of the position corresponding to the rst digit of the subscribers in the second series, wipers T1 of CO, RMS, T23, R64', R53, windings of the relay 8- and battery. The relay Il is not energized onf: account` of.' the. high resistance-1` of the winding of the relay I4.

'Ehe-"relate K4isenergizedrandicloses'itsholding circuit ati- T`I 41I" through its.- nerr-inductive lower winding;

The: sequenceoff operations previously: described ist repeatedf but the wipers' A23. 'llzg TR2, take the place of the wipers Au.Bi,.T, TRL.

Communication with thief outside network.- Wh'ema :calli emanatingfrom the; outside network isi received. on the conductors; of the` linetLi-Llz (Fig. 3), ringing currentisereceived by the relay. 43!" viaff the circuit: conductor' L1,. R421.; R452, winding ofthe relayr 46;'ccnd`enserz Cn3fandi con'- ductor LaV The' relay 4.6' closesfthe:followingfcircuit ot the, relay' 4-6: batteryh.` RTI-I, windings. 46; T462", R39I and earth. The relay llizloclisfup'fviac; '11464,v R452 and eartli.` It closest the-` circuit' of: relay 24e inseries: with the'` ringing. lamp= through'. T4651. The; relayl 21 is energized', and. throughl T21I`l; short-circuits-its lowerY windingwhich: cau'seslthe calling. lamp to: l-ightl up through' its low' resistance: upper windings: Throughi 'n22i-2. it. corn'.` pletes the ringing; circuiti So.

WhenY the.l operator. depresses the listening key assigned to the outside line which is calling,. the*` following. circuit for the relay' 3-6l is set. upc. batterm.. windings of 3a in seriesg. spring: ot the network listening key,` andf its operating.. contact, resistancefRf andeart-h; The relay 36 short-cir.- cuits 'Y at T361 its.. high resistance lower winding an'df. holds onA itslow resistance `upper winding. Thisarrangementis provided topreyent two lines. of the outside net-Work",` beingconnected` simulta-neouslyfwhen` the two: network listeningf keys aredepressed; 0n account. of theresistance: of` therelay 36- and the presence of the; resistance R5 in the circuit, no two relays 36 can be energzedl..

The following. circuit of the1frelay3I is closed: battery, upper windings of 3I and 33, R343, T364,` service stationePS;` T365, R342, lowerwinding,4 of

33 and 3-Iv and. earth;` The relay' 3Ii` is energized;

but. thelrelay 33, Whosetwovwindings-are;` in opposition, does not operata. Through: 3fI-I4 the relay 3I closes the circuit of t-he'relay4 45, as'follows;` earth; Winding` of 45", TiN-I,` non-inductive upperwindingof 39` and battery;

The. outside lineA isheld by the following, ciror reiayfsu 'ral-2, conductor L2;

The ringingA circuitis opened at R452, and. the: circuit of the relay 46 at R45'2`."`. Therelay, 46` falls off, dpeningthe circuit of the calling lamp and of the relay'Z-I, which opens theringing cir-- Whenthe outside subscriber has informed the P'.- .B-1i' operator withH whom he desires' to 4be connected, the` operator depresses the transfer key. earth is thus' applied' through T364 and R343 to the upper winding of 33, the lower` Winding being.thensliort-circuitedl The relay 33 will noW pullulp andclo'sesl the following circuit of therelay 42: battery, upper Windingof 42, T33I', '114.520` and earth.

` Vifherifthe operator releases thertransierr'keyf,

the relay 33 whose two windings are then fed, releases.

The relay 42, which is slow to release, remains up for a suflicient time to permit the relay 32 to become energized in the following circuit battery, winding of 32, R382, T422, R33I, T452' and earth. The holding circuit of the relay 42 is completed through T322 and T452.

When the relay 42 is energized, the outside line is disconnected from the operators station PS, and held via: conductor L1, T425, resistance R1, T3l2, conductor L2.

The relay 32 is then held and via T324,7R345, wire M1 and applies earth to one of the ends of the windings of the relay I I, which causes a local finder CH to be put into operation, as has already been described in the case of a call between P. B. X subscribers.

When the wipers of CH reach the bank contacts of the outside line used, e. g. az, b2, t2, trz, the following circuit of the relay 34 is completed: earth, winding of 34, shunted by resistance R8, T325, wire t2 in the cable V, bank contact tz of CH, TI I4, windings of I in series and battery.

The relays 34 and I Il are energized in series and the relay I0 causes the line finder CH to stop.

Through T34I, the relay 34 completes a holding circuit for the relay 3l through the resistance R9. At R345 it disconnects earth from the wire M1. At T342 and T343 it connects the station PS to the wipers A and B of CH via wiper A of CH, bank contact a2, wire a2 of the cable V, T343, T364, station PS, T365, T342, wire b2 of the cable V, bank contact b2 and wiper B.

The operator at the station PS can then communicate with the called P. B. X subscriber, e. g. P1, as has been described in the case of a local call.

The operator advises the subscriber P1 that a call intended for him is waiting on an outside line. i

The subscriber P1 then presses the transfer button TF on his set. An earth is thus applied to the wiper Ai'of CO and causes the relay 9 to operate, since its lower winding is short-circuited. The following circuit for the relay I5' is completed: earth, T92, winding of I5', TI03, wiper DA of CH, bank contact da, wire da1 of the cable V, winding of relay 38 and battery.

When P1 releases his button, the relay I5' is held by TI5I. The relay. 38 is not energized in the circuit indicated on account of the resistance of the winding I5. v

The relays I3 and 22 are energized in the following circuit: battery, windingsin series of I3, R9I, TI52, wire T, winding of 22 and earth. The relay I3 is held by TI3I on its upper low resistance winding in order to prevent two transfers occurring simultaneously on the same line.

The energizing circuit of the relay 40 through its upper winding is set up as follows: battery, upper winding of 40, T45I, R4II, T344, wire tra of cable V, bank contact trg, wiper TR of CH,

R32, TI32 and earth. The relay 40 completes the following circuit of the relay 39: windings in series of 39, T40I, contact of the electromagnet RCR of the switch CR, R31I, R35I' and earth. The relay becomes energized and lcloses the circuit of the electromagnet RCR of the switch CR as follows: battery, winding of RCR, T392, R31I, R35I and earth. f

The electromagnet RCR attracts its armature and thus opens the circuit of the relay 39, which drops and at T392 opens the circuit of the electromagnet RCR which releases its armature. thus causing the wipers of CR to advance by one step, whereupon 39 is again operated and closes the circuit of RCR. The same operations are repeated and by the play of the relay 39 and of the contact of the electromagnet RCR the wipers of CR advance step-by-step.

When the wipers of CR reach the bank contacts which `correspond to the station line P1, the relay 31 is energized in the following circuit: battery, windings of 31, T496, wiper TR of CR, wire tr of the cable U and of the cable V, bank contacts t1" and wiper TR1 of CO, RI42, T82, resistance RIU, TI33 Iand earth.

The relay 35 is energized in series with the relay C of the station P1 in the following circuit: battery, winding of 35, T313, wiper T of CR, bank contact t and wire t of the cable U, bank contact t of CH, TA1, winding of C and earth.

A circuit for the relay 38 and a short-circuit for the relay I5 is closed via: earth, T32I, T355, and T434. The relay 38 is energized and completes its holding circuit via: T33I, T422, R33I, T452 and earth.

The relays 32 and 42 fall off, their circuits being opened at R382 and at T332. Relays 34 and il] drop, their circuit being opened at T325. The relay 38 drops, its energizing circuit being opened at TISS and its holding circuit at T422.

The relay 31 drops, its circuit being opened at TI32. The relay 2 drops, short-circuited by RI I, and the earth at RI5I'.

When the relay I9 has dropped it opens the circuit of the relay `I, which drops and causes the release of the local circuit, as has been previously indicated.

The relay 4U is held on its lower winding by: T4512, T362 and R32I.

When the relay 32 has been released the operators transfer lamp lights up, advising the 0perator that the transfer has been effected. The operator then releases his outside line network listening key which causes the relay 36 to be released. The relay 40 drops, its holding circuit being opened at T362 and the transfer lamp is extinguished.

The subscriber P1 is from then on in communication with the external network via: conductor L1, R421, T452, R343, R364, T354, wiper A of CR and bank contact a, wire a in the cable U, conductor I1, station P1, conductor I2, wire b in the cable U, bank contact b and wiper B of CR, T353, R365, R342, R426, T3l2 and conductor L2.

The subscriber station P1 is fed with current through the relays 3I and 33.

At the end of the conversation when the subscriber P1 replaces his handset, fthe relay 3| drops. The relay 45, short-circuited at RSI I, drops and again connects the outside line L1-L2 to the calling relay 46'. The relays 35 and C drop, their common circuit being opened at T453.

The outside line L1-L2 is released when T3I2 opens.

When a P. B. X subscriber wishes to enter into communication with an outside subscriber, he may either ask `the P. B. X operator to call the outside subscriber, or he may make this call by connecting himself directly to an outside line.

First, I shall explain how an outgoing call is established by the P. B. X operator.

The P. B. X subscriber such as P1, liffts his handset and then proceeds as in the case of an inside call to dial the number of the line I"1-I 2 of the P. B. X operators station. The wipers of 9 ji CO stop on the bank contacts 1a1,` b' 1, t1,:tr'1',fto which the said line is connected.

The ringing current is transmitted `overth'e conducto-rs |1-|2 and-operates' relay 24' which closes the circuit of relay 24: battery, winding o'f 24, T24 rest contact and spring-1| of the""night service key and earth. The relay 24 is `operated and via T241 completes its holding circuit independently of the relay 24'. It completes `via T242 the circuit of the calling lamp 1in series with the relay 2l. The relay 2| operates and at T21|| short-circuits its lower high resistance-winding. The calling lamp lights up. At T2l2, the relay 2| completes the ringing circuit S01.

The operator depresses the line'service listening key. The circuit of the relay 26 iscompleted through the resistance R5. Via T26| and'I262, the relay 26 connects the lines |1-|2 to the operators station PS. At R264 itopens the circuit oi 24 which drops. The calling lamp iseX- tinguished, the relay 2|' drops and opens theclrcuit of SO. l

Through T233 the relay 2li short-circuits-its lower high resistance winding, but is held by its low resistance upper winding. 'This arrangement prevents any possibility of confusionY on an outside line if the two listening keys `were depressed simultaneously. In this case,the relay 25 could not be energized.

The subscriber P1 is n-o-w connected withthe P. B. X Operator. He gives the number'vof the outside party to whom he wishes tol be connected, and replaces his handset'. Theoperator releases the listening key and the service line |1, |52, and the equipment of the P. B. `X automatic switchboard is also released.

In order to call the Voutside ,subscribeigthe perator depresses her outside network listening key. Relays 36, 3! and 45 are energized, as -was described in the case of the reply to a call originating from the outside network.

The connecting loop of the-outsideline is com,- pleted via: conductor L1, R421, T452, upper-winding of relay 4l, T3|2 and conductor Le. A

When the P. B. X operator at PS receives the dialing tone of the outside automaticexchange, she proceeds to dial the called subscribersnumber which operates relay 3| in the'rhythm of `"the` impulses. Upon the first de-energization of relay 3| the following circuit of relay 39 is closed: battery, windings of 39, R49l, T453', R3|| and'earth, and this relay operates.

Upon each operation of 3| its lower Vwinding is short-circuited at T3| l whereby the relay is suiliciently retarded not to release during impulse sending. The same thing applies for 'relay 45, which is also retarded in its release.

The circuit forthe transmission of impulses to the outside network is as follows: `conductor L1, R421, T452, T393, resistance R1,shunted by the upper winding of 4|, T3|2 and conductor L2. The interruptions are repeated -in this #circuit by the opening of T312 of relay 3|.

When dialing has been completed, the relay 39 drops, and the relay 45 is held by T3|| across the upper non-inductive windingof '39. 4

When the called subscriber answers, the P. .BgX operator is placed in communication with ,the said subscriber and the transfer of .the call .to the calling P. B. X subscriber takesplace in the manner as in the case of the Ttransferfoflatrin-V coming call.

I shall now explain how a P. B. X subscriber can get into communication with an outside fsubscrber :without the services of the l?. B. X operator.

.Assuming that station'P1 lifts his handset, the finder CHand connector CO are operated as has been previously explained. When he receives the dialingrtone,"P1 depresses the button TF of his set. This short-circuits the lower winding vof the relay -3 and this 4relayV operates.

Therelay |5 is operated over a circuit via T31 and is held after the release of 3 by T|5|, T24 and earth.

V'Relay3 falls off when the subscriber P1 releases his button y'IT'.

The-following circuit for relays 8 and `23 is set up: battery, windings in series of 8, R53, R64, T23, RI43, wiper T1 of CO on the rest position, T|54,.R33, resistance Rl l, wire M, relay'23, R223, R223,-R46|, R42|,1R45'| and earth.

lAtR85 'the relay-8 opens the dial tonecircuit The jrelay23 closes `the following circuit for the relay4ll: battery, upper Vwinding of 45, R45|,

The `circuit of the relay '39 is established via: battery, windings in series of "39, T43I, contact 0f the electromagnetfRCR,YR31 I `R35l, and earth.

At'I-'392 the relay' 39 4completes the circuit of the electromagnet 1 RCR.

From Vthen on, as 1a result of the play of the relay 39 `and the .electromagnetRCR 4the Wipers of CR will advance step-by-step, as has previously been explained,

When the wipers `of CR reach `the `bank contacts ofthe line of `the station-P1the following circuit ofthe Vrelay'3-'I1is completed: battery, windings1of-relay131,'T4ll6,`wiper"TR of CR, wire TR in the cable U, wiper TR- of CH, R32, R43, R31, T|53,`Rl53,resistanceR|0, T82, Rl42, wiper TR1 of'COonthe rest position, wire T5, R22l, R22| andfeart-h.

":Therelay 31 at 'R3-1|, opens the circuit of the electromagnet RCR and the relay 39 and the wipersof CR stop.

The relay 35 is energized in the following cir cuitlbattery, winding `of V35, T313, wiper T of CR,

`bank contact t and wire t `of cable U, TA1, relay C1 and earth.

Relay l0, shortcircuited `by thelow resistance offtherelay 35 drops, opening at T104 and T|-ll5 the circuit of relay which releases .thelocal 'zir- `cuit. lRelay l5 `drops `when its-holding circuit is openedat T24. Relays -8 and `23 drop, their circuit-being opened at T154 and T23.

The following `circuit for relay 31 `is closed: battery, upper winding of 3|, upper winding of Y 33, R343, R364, T354, wiper A -ofCR, wire a of cable U, 'conductor |1, calling station P1, conductor I2, wireb of ycable U, wiper B, T353, R355, R342, lower winding of 33 and 3|, and earth.

Via `T3|| relay 3| completes the circuit of 45 through the upper `non-inductive winding of the relay 39. 1 `When the relay 45 is energized the connecting `loop ofthe outside network line is completed via: conductor L1, R421, T452, upper winding of 4|, R426, T3l2, and conductor L2.

When the subscriber P1 Yreceives the dialingtone coming from the outside automatic switchboard he operates his dial whichproducesinterruptions in the circuit ofrelay 3|.

The impulsesare repeated on 'the outside line inthe same way as when the dialing was by the operator vofthe station PS.

The relay 31 drops when its circuit is opened at TI53. The relay v35 is held by T352, T453, R323 andearthon the wiper TofCR. The relay 40 .falls .offwhen its circuit'is opened at R45I.

When conversation is completed and the subscriber P1 replaces his hand-set rst the relay 3l de-energizes and then relay 45. 'Ihe line L1-L2 is released as soon as T3I'2 is opened. The relay 35 drops, its circuit being opened at T453.

The equipment used in the direct connection with the outside network is released.

The P. B. X subscriber may during conversation with the outside network hold the outside line and call another P. B. X station. It is then possible either to continue the conversation between the outside line and the first P. B. X station or to transfer the call to another P. B. X station.

A subscriber such as P1, being in communication with .the outside network through the line Li-Lz relays I5, 3| and 45 are energized.

Without abandoning the outside network, P1 may enter into communication with another P. B. X subscriber by switching the call from one operator to another operator to whom the subscriber then passes his request. In order to do this he will press the button TF on his set. This operation results in the application of an earth to the wiper A of CR. The relay 33 is operated and then follows the sequence of operations described in' connection with the transfer key: the relay 42 is energized, the relay 33 drops, the relay 32 is energized, the line L1-L2 is held, a local finder is started, the finder CH is stopped on the bank contacts of the outside line Li-Lz, and the relay 34 is energized. The relay 35 is held by R403.

The subscriber P1 is connected to a local nder via: battery, upper winding of the relays I and 3, TI05, wiper A of CH, bank contact a2, wire a2 of the cable V, T343, R364, T354, wiper A of CR, bank contact a, wire a of cable U, conductor I1, station P1, conductor I2, wire b of cable U, bank contact b and wiper B of CR, T353, R365, T342, wire br of cable V, bank contact br andrwiper B of CH, TIM, lower winding of 3 and of I and earth.

The subscriber P1 may now callanother P. B. X station.

If P1 wishes to continue the outside conversation he again presses the button TF on his set. The relay 3 is energized and earth is applied to the wiper A of CH. At T3I the relay 3 closes the circuit of relay I which closes its holding circuit via TI5I and T24.

When P1 releases his button TF, the relay 3 drops and closes the following circuit of relay 38: battery, winding of 38, wire da of cable V, wiper DA of CH, Tlll3, TI52, R3I and earth. The relay 38 completes its holding circuit over T38I, T422, R33I, T452 and earth.

'I'he circuit of relay 34l is opened at R382 and that of relay 42 at T322, relay 32 being de-energized when 382 opens. The relays 34 and II) drop, their circuit being open at T325. The relay 38 drops, its circuit being open at TI03, and at T422. The local circuit is released after the drop at I0.

After the drop of 34 and 42 the subscriber P1 is again connected to the line Ll--Lz of the outside network.

A P. B. X subscriber may transfer a communication from the outside network to another P. B. X subscriber. After connecting the other P. B. X subscriber by having the call switched by one operator to the other to whom the subscriber can then state his request, P1 asks the other P. B. X subscriber to take over the call which is being held on the line L1-L2.

The second P. B. X subscriber then presses on the button TF of his set, and the same operations are performed which have been described in de- 12 tail in the case of the routing by the P. B. X operator of an incoming call. The relays 9, I5', I3, 22 and I40 are energized. The relay 35 and the relay C of the station P1 drop. The relay I v drops. The relay 39 is energized, as is the electromagnet RCR which advances the wipers of CR by the play of the relay I9 and of the contact of RCR.

When the wipers of CR arrive on the contacts of the line of the second P. B. X station, the relays 3'I and 35 are energized in series with the relay C of the said station. Then follow the energization of 38 and short-circuiting of relay I5', and the drop of relays 32, 34, 42, IE) and 38. The circuit of 40 is opened at T344 and of 3l at T3I2. Relay 2 is short-circuited by RII and the earth at RI5I.

The local circuit is released and the second P. B. X subscriber is connected to the outside network when the relay 35 is energized and the relays 34 and 42 drop,

Restricted night service-When the operator of the P. B. X service station leaves her station she depresses the night service key When an outside call is received on the line L11-L2 relays 46', 46 and 2| are energized as previously described.

Via T2I3 the spring I of the night service key, and its operating contact, an earth is applied to the wire of the repeating bells at the P. B. X.

Any one of the P. B. X stations may then connect with the line L1-Lf.. In order to do this, the subscriber will lift his hand-set and dial a certain number, 0, for example. He will then press the button TF on his set.

A free line-finder CH and connector CO are connected with the P. B. X line which answers. When 0 is dialed the wipers of CO advance to the tenth position. The following circuit of the relays 8 and 22' will be closed: battery, windings of relay 8, R53, R64, T23, RI43, wiper T in position IIJ, bank contact n of CO, wire N, spring 2 of the night service key and its work contact, relay 22', T46I, R4'2I, R45I and earth.

Relay 40 is energized over its upper winding via: battery, upper winding of 4t, T463, R222', T222 and earth.

After the energization of relay 4I] the line Li-Lz will be connected to the P. B. X station Which-answers as in the case of a transfer.

In this case the circuit of the relay 3l is as follows: battery, windings of relay 3'?, T405, Wiper TR- of CR, wire tr of the cable U, bank contact tr and wiper TR of CH, R32, R46, RSI, TI 53, resistance RII), T82, RI42, wiper TR1 of CO on position 10, wire TN, T22I R22I and earth.

The release of the local circuit and the establishment of the connection proceed in the same way as previously described.

Y It will be noted that when the relay 45 is energized upon the receipt of acall from the outside network, the following circuit of the thermic relay TH is completed: battery, contact and winding of the thermic relay TH, T462, R45I', work contact and spring I of the night servico key, and earth If, after a certain lapse of time which is dependent on the operating constants of the relay TH no P. B. X station answers, then the thermic relay TH opens in its contact, the circuit of the relay 46 which drops, and at T435 opens the circuit of the relay 2|, which in turn opens at T2I3 the circuit of the repeating bells,

If the call persists when the relay TH verted to rest position the relay 45 will again be 1:3 attracted .and 4the sameztoperations Lare. repeated.

It should be noted that when a.P.` B. X `subscriber dials-the number for A.directly answering an outsidecall when the night service keyV vofthe -P..'B.X operators stationhas not been depressed,

.be set up: earth, upper winding oiA E, T52,"T2'3, R143, `wiper T1, `bank `contact `wire N, Vspring 2 and rest contact of thenight servicekey; resistance R52 and battery. The relay -6 is energized and the calling signal isr transmitted to the P. B. X subscriber.

Forced listening-:When an operator at .the P. B. X service station routes an outside call by switching it to anotheroperator to whom the outside party repeats his request, then if the called P. B. X station is busy, the second operator would normally receive the busy signal. She mayA then break into the call as a third party to advise the called P. B. X subscriber that an outside call is waiting.

For `this purpose she operates the forced listening key and thus via T383 completes .the circuit of the lower winding of the relay 4l, which operates. The following circuit of the relay 4 is then completed: battery, winding of `relay 4, TSI, R 48, R32, wiper TR ofCI-I, bank Contact trz, wire W2 in the cableV, T344 and earth. The relay 4 completes its holding circuit `via T4I, resistance R3, T24 and earth.

The circuit of the relay 8 is completed: battery, windings of S, R53, T64, resistance Rl3, T45 and earth.

`Via T81 and T88 the P. B. X operator of the service station is placed in `communication with the P. B. X stations through the finder CH and the connector CO.

Nevertheless, in .order to advise the two P; BIX subscribers that the P. B. .X operator will cut` in on the call an attenuated busy signal is applied to the line by T82 through the high resistance Rl4 which in this case is not short-circuited at R43.

If the `called`P.B.-X station accepts the `outside call he `presses the `button TFon his set and the operations take place as previouslydescribed.

`Figure 4 shows adiagram of a relay automatic P. B. X switchboard. It is assumed by `way lof example, that this automatic switchboard accommodates siX local subscribers and one outside line. It is clear that the number of local stations and outside lines can vbe increased without departing from the spirit o'f the invention.

When a subscriber such as BPl wishes to `call another P. B. X subscriber such as"BP2,"he removes his handset, whereupon he is connected with the connector BECR through one of the junction lines B-Ji or B52. He receives the dialing signal and dials BPzs number. If BP2 isdisengaged the connection is completed by the equipment BECR through the connecting line BJc. When BP2 answers, the two subscribers are connected'through the junction line BJ 1 or BJz. The connector equipment BECR is released, the connection being supplied with current from lthe equipment BAL.

When a subscriber such as BP1 :wishes to communicate with an outsideiine and removes his hand-set, and is connected to the equipment BECR through the `line BJi or BJz, then upon the receipt of the dialing tone he depresses a button on his set which results in a transfer of the call to the equipment BELR associated with the outside line. The equipment BECR is released `and BP1 is connected to the outside` `network through BELR.

VWhen a` station such asBPr is connected `with ganioutside llinefand itfisdesired to have one opferatorgput afcall through to `the'other operator to whom' the subscriber 'then `makeshis request, BP1 presses the button on 'his set. Inthe equipment 'BELR "the outside line-is held and the junction f line BJ 1 orrBJzfiis-connected to BECR. BPr dials-'the number offthe P. B. X subscriber whom he desires .-tocall; BP2 for example. When AilfPz-answers,his station willlbe connected with P1 .over one of the .circuitsBJrorBJa the equipment JBECR0 andthe circuit YBJ C.

.lnV ordereto recall the outside line, `BPi presses the-button on *his set once more which in. BECR cuts off the local call and connects BJ 1` yor-BJz to .BELR. Inprder to transf-er -a call on the outside line, their-station BPriirst causes Aone operator to pass .tl'ie-:calltto --another operator to .whom thesubscriber then makes his request, e. g: that the subscriber BP2 be informednthat there is an outside callOrhim. The, subscriber BP2 cpresses the button-formingpartlof `his seti/which causes in the equipmentfBElCR.thedisconnection of the'station YBPr from the'circuitBJ 1 or YBJ 2, the connection of th'estation.-BPzfto` ,the said circuit, and the con- `nectionaoffthis circuit to thefnetwork equipment `BFLR.- Y

Adetailed explanation shallnow be given with referencetoEigures 5.and16 ofthe operation of thisrelay automatic switchboard.

`Localcall-.When ya- P. B. Xsubscriber such as BP2 removes his.handset the following circuit is YIclosed for the relay-BSH battery, winding of B9', R69l', `Rllll', R29i', conductor Blz, subscribers station BP2; conductorBl 1, R233', R492', RSS2', .andearth `.The relay B8' isoperated and at'T94' completesihe. circuit of the right-hand winding of 'the relay .-B18,fwhich is-operated because .its .lefthand-fwinding is energized over T33' through a resistance .i BR1.

The following circuit of the relayB21 is then .closed:..battery, lower winding of relayB21, R282, R254,iwire d, R412, fR24l,iwir.e i, TSI', TBI and earth. The rcircuit; for the right-handwinding of the relay B29 is closed yvia: T214, T92', T82 and earth. Via T214' the relay B21 completes the circuit of the relay B41 which operates.

'I'he relay B9' drops, its circuitbeing opened at R291 andr-R293'. The relay B8 drops when its circuit is Iopened Sat T94' and the relay B21 when its -circuit .isopened Aat R412. The ,following circuit for relay B63 is closed: battery, upper windings of B63 and B64, R85l, T41I, R25I, T291, conductor I 2, subscribers station BP2, con- .ductor"l1, T293', R252, T414', R853, lower windings of B64 and B63, and earth.

The relay B64, whose two windings arein op- ,.positionandrare inserted in the same circuit is .not energized.

.The circuit of relay B83 is completed as follows: earth, winding of B83, T63I, upper non- .inductive winding ,fof B84 and battery.

,-,fAgholding circuit-for the relay B41 is closed :via: T484, T413, R61l', T83| and earth. A hold- `ingcircuit `forthe relay B23' is closed via: T292', T413', R812, T832 and earth.

' "The :dialtone is sent to the calling subscriber -vviia'rs1't812,fcondenser Cm, T414', R252, T293 and .andthe subscriber station BP2.

*'Whenithe 4subscriber BP2 dials the number of fthe called subscriber the circuit of the relay B63 is interrupted. When the relay B83 drops for theirst'f impulse of` each impulse series the relay `H84 isenergiZedvia: battery, windings in series of B84, R814', T835, R63I and earth. At each operation of B63, the lower winding oi B84 is short-circuited, which retards the said relay sufiiciently that it will not be released during the reception of an impulse series.

Upon the reception of the rst impulse series the relay B88 is energized over its left-hand winding via: battery, left-hand winding' oi B88, R88I', T843, R632, T834 and earth.

When the relay B63 is again operated after the first impulse the relay B88 is held in series with the relay B88' via T88I and T834. The following circuit is then closed for the relay 89: battery, winding of B89, R892', R902', R9I2, T882, T834 and earth.

After the first impulse has been received the following circuit of the relay B81' is completed: battery, winding of B81', R815', T843, R632, T834 and earth. The relay B81' completes its holding circuit over T81I', T83I and earth and at R812' it opens the dial tone circuit.

When the second impulse is received the relay B88 becomes de-energized because current ows through its right-hand winding via: T88I', T834, R632, T834 and earth. The relay B88' is held in the same circuit by its right-hand winding.

When the relay B63 is re-energized after the second impulse the relay B88' drops, its circuit being opened at R632 and it closes its contact R883 at the same time as it opens its contact T882'. The following circuit for the relay B89' is completed: battery, winding of B89', T892, R902, R9I2, R883', T834 and earth.

The relay B89' opens at R892' the circuit of the relay B89 and locks up via T89I', at T892', preparing the circuit for relay B90. Upon the reception of the third and fth impulses, relays B88' and B88 are energized again, as has been explained for the reception of the first impulse. Upon the reception of the fourth and sixth impulses they drop, as upon the reception of the second impulse.

It will be seen that by the play of the relays B88, B88', B89 to B9I and B89' to B9I' upon completion of dialing only the following relays will remain attracted:

B89 if the number dialed is 1 B89' if the number dialed is 2 B90 if the number dialed is3 B90' if the number dialed is 4 B9I if the number dialed is 5 B9I' if the number dialed is 6 Each of these relays prepares the circuit for the one which follows and opens the holding circuit of the one which precedes.

It will be assumed BP2 wishes to enter into communication with'BPs. He dials 6, and on completion of the dialing the relay B9I is operated and holds over T9II', R883', T834 and earth.

If the called subscriber BPs is free, the following circuit is closed for relay 1I' when the relay B84 drops for a minute after the completion o f dialing: battery, winding of B1I', TI96', R68I, R842, T83I and earth.

Ringing current is transmitted to the called subscribers station via: earth, secondary winding of the transformer R864, T112', Rsls', R3I3,

conductor I1, condenser, bell at station BP6, conductor l'2, R3II', R5II', 'I1II', R863, winding of the relay B86 and battery.

The relay B86 which is insensitive to alternating' current remains operating when the subscriber BPS lifts his receiver and locks up via: resistance R2, T86I, T83I and earth.

The following circuit for the relay B65 is completed: battery, upper windings of B66 and of B65, T863, T1I I', R5I I', R3I I', conductor I1, station BP6, conductor I'i, R3I3, R5I3, T1I2', T864, lower windings of B65 and B66 and earth. The relay B66 whose two windings are in opposition does not operate.

The relay B3I is energized over the following circuit: battery, left-hand winding of B3 I T9 I 3', T412', R81I', T65I and earth. The relay B25 is energized in the circuit: battery, winding of 25, R266, T415', R814, R845, R81I, T65I and earth. The relay B25 opens the circuit of the relay B63 at R25I and R252. The relay B83 is then shortcircuited at R63I and drops after a short while. The relay B65 drops, its circuit being opened at R3II and R3I3'. Relays B41, B1I', B86 and B81 drop, their circuit being opened at T83I. Relay B9 I drops, its circuit being opened at T834.

Relay B46 which feeds the stations BP2, BP6 via T25I, R682 and via T252 and R684 is operated. The relay B25 is held via R266, T255, T46I and earth. The relays B29 and B3I are held by their right-hand windings, one via T293' and the other by T3 I3 on the earth of T253.

The talking circuit between BP2 and BP6 is as follows: BP2, conductor I1, T293', T3I3, conductor Ii, BP6, conductor I1, T3I I', T29I, conductor I2 and BP2. The two stations are fed in parallel through the windings of the relay B46, as has been described. Upon the completion of communication when the subscribers BP2 and BP6 have replaced their hand-sets the relay B46 drops, opening at T46I the circuit of the relay B25, which drops. Relay B25 at T253 opens the circuit of the relays B29', and B3I which drop. The release is completed.

VIf the subscriber BP6 is busy the following circuit for the relay B68' would be completed: battery, relay B68', T84l, T9I5, T3 I4 and earth.

The busy signal will be transmitted to BP2 via the circuit: T684', R862, condenser Cnr, T414', R252 and T293.

In this P. B. X automatic switchboard provision is made for the interconnection of six stations and for one outside line Iii-L2. Two junction circuits BJI and BJ2 are provided within the P. B. X. Usually only one junction line will be needed for local calls, the other remaining available for outside calls.

If one of the junction lines is engaged by a local call between two P. B. X stations, and a third P. B. X station wishes to call another P. B. X station, the same operations as previously described take place when the calling station lifts his hand-set, until the busy tone signal is transmitted.

When the calling subscriber dials the number of the called subscriber, as soon as the first impulse has been received by the relay B63 and this reslay operates, it closes the circuit of the relay B 1.

The relay B416 closes the following circuit for the relay B68: battery, Winding of B68', T813', R813, T462 and earth.

The relay B68' opens at R68I the circuit of the relay, such as B69 of the called subscriber. It completes the circuit for the transmission of the busy signal to the calling station via T684' and R862 and at T683' it prepares its holding circuit which will be closed upon the completion of the reception of dialing impulses via R844, T83I and earth.

19 pletes the following circuit for relay BEQ': bat'- tery, left-hand winding of B29', T893', T1172', TSlI, T854 and earth.

The relay B29 opens at RZQI and R293' the circuit of relay B555, which drops. Relays B?, B85, B57 and B86 drop, their circuit being opened at Tii and T552'. Relay B81 drops, its circuit being opened at TM. The circuit or the dialing relays is opened at 'I'.Sil'.

The station BP2 is now connected with the outside network Via: station BP2, TZSI', RZEI, RMI', T243, TIIII, conductor L1, outside network, conductor L2, T2I2, TME, R'ili', R252, T293' and station BP2.

The station BP2 may control the switching of the call from onestation to the other in the same way as has been described for the station BPI.

If the P. B. X station wishes to call an outside subscriber the same operations are performed as when PI answers an4 outside call land thus obtains connection with the line Li-La When the calling subscriber receives the dial tone from the outside network he dials the number of the called subscriber. The relay B2I, whose circuit is interrupted at each of the dialing intervals, will beat in the rhythm of the dialing impulses.

When the rst impulse of each series is received, fthe relay B42 is energized via T4I2, RZII and earth. It is held while the impulse series lasts, its winding being short-circuited at each operation of B2I. The relay BM' is slow and remains attracted during the impulse series.

At TMI the relay B42 inserts the resistance RI3 in parallel with the self-inductance 23 and the dialing impulsesV are re-transmitted to the outside network by the opening of the loop of the line Li--Lz at T2I2.

It will be noted that in the course of a call made by the station BPI with a View to electing the transfer of an outside call this station receives the busy signal, because the called station is engaged in a P. B. X communication.

A busy station may be apprised of an outside call by depressing a listening-in button EF which is provided only ait station BPI. The following circuit is closed for relay B68: battery, winding of BES, T682', TM5, wire c, T295, button EF and earth. The relay BES closes its holding circuit at T683, T83I and earth and a circuit for relay B86: battery, winding of B85,v T585, T83I and earth. The circuit of relay B55 is opened at R682 and RSM. The relay B65 is energized by: T863, T682 and via T864 and T684 through the 'two stations in parallel which were previously fed by the relay B46.

The station BPI is connected in parallel with the call while it is in course of being established. In order to prevent listening-in by a. third party on two subscribers in conversation, an attenutated busy signal is applied to the line T684' through the high resistance RI5, which is shortcircuited at R862.

The P. B. X service station BPI advises the called P. B. X subscriber of the waiting outside call. When the local call is nished, the connection between the service staltion BPI and the called P. B. X station, as well as the transfer of the outside connection take place. It will be noted that if a P. B. X station dials a number which is grealter than six where only six stations are provided, the relay B58 will be energized via: T9I2', T882', T8311 and earth. The calling subscriber will then receive the busy signal.

What is claimed is:

1l In a telephonesystem, a private branch exchange, a plurality 'of subscribers stations connected with said exchange, means including a numerically operable switch and controlled by a cal-ling station for establishing a connection between it and a called station, an outside line terminating atthe exchange, means including said automatic switch `and controlled from a calling station Yfor connecting it with said line, and other means also including said automatic switch controlled by a station for connecting the outside line with any one of said stations.

2. In a telephone system, a private branch exchange, a plurality of subscribers stations connected with said exchange, a first and a second line finder switch, and a connector switch at the exchange, each of said switches having a bank of terminals and cooperating wipers, a connection between the wipers of each iirst line nder and a connector, multiple connections from the terminal banks of all said switches to said stations, an outside line terminating at said exchange and connected to the wipers of the second line finder, a connection from the terminal bank of the connedtor to said outside line, and a connection from the terminal bank of the irst line iinder to the outside line.

8. In a telephone system, a private branch exchange, a plurality of stations connected with said exchange, a special service position in said exchange, an outside 4line terminating at said position, means including automatic switches for establishing connections between calling and called stations, means at said positions for controlling said switches to establish a connection between the outside line and any one of said stations, and means at said position for controlling said switches to transfer said last-mentioned connection from one station to another.

4. In a telephone system, a private branch exchange, a plurality of stations connected with said exchange, an operators position in said exchange, an outside line terminating at said position, means including automatic switches for establishing connections between calling and called stations, means at said position for controlling said switches to connect the outside line with any one of said stations, and means at said stations for controlling said switches to connect the outside line with any station.

5. In a telephone system, a private branch exchange, a plurality of stations connected with it, a special service position, an outside line terminating thereat, a first, a second and a third switch, multiple connections from all the three switches to the stations, means responsive to the initiation of a call on one station for connecting it over the first with the second switch, means at each station for operating the second switch to connect with any other station, means at said position for operating the third switch to connect the outside line with any station, a key at each station, and means responsive to the actuation of said key after the connection of the associated station with the second switch to actuate the third switch to connect with the station.

6. In a, telephone system, a private branch exchange, a, plurality of stations connected with it, a special service position, an outside line terminating thereat, a first and a second finder switch and a connector switch, each having a bank of terminals and cooperating wipers, connections from the wipers of the rst finder switch to the wipers of the connector, multiple connections from the banks of all the three switches to finder the stations, a connection from the wipers of the second iinder switch to said position 'and therethrough to said outside line, means responsive to the initiation of a call on one of said stations for operating a first finder switch to connect the callingline with the wipers oi said connector, means attheposition for operating the second switchto select the terminals of any station, a key at each station, and means responsive `to the actuation'oi said key after the connection of `the vstation with the connector through the 'rstunder-switch to actuate the second finder switch to select -the station.

7. In a telephone system, a Vprivate branch cxchange, a plurality of stations connected with the exchange, a service position at the exchange, an outside line terminating at said position, a iirst, a second and a third switch, multiple `connections from all said switches to the stations, a connection from the service position to the first switch, means controlled by the stations for operating a rst .and a second switch .to .establish connections "between a station. and the outside line, a first key at the service position, means responsive to the actuation thereof to hold the outside line and to connect a station through the rst switch with the second switch, a second key at each station, means responsive to the operation of a second key for connecting the associated station through the third switch and the service position with the outside line, and means at the position for releasing connection through the rst and second switches.

8. In a telephone system, a private branch exchange, a plurality of stations connected with the exchange, an operators position at the exchange, an outside line terminating at said position, a rst and a second finder switch and a connector switch, each of said switches having a bank of terminals and cooperating wipers, multiple connections from .the banks of all said switches to the stations, a connection from the operators position to the bank of the first finder, means controlled by the stations for operating said switches to establish a connection between a station and the outside line, a key at the operators position, means responsive to the actuation thereof to hold the outside line and to connect a station through the rst finder with the connector switch, a second key at each station, means responsive to the operation of a second lkey for connecting the associated station through the second finder and the operators position with the outside line, and means at the operators position for releasing a connection through the first under and the connector.

9. In a telephone system, a private branch exchange, a plurality of stations connected therewith, an operators position at said exchange, an outside line terminating thereat, a connector at the exchange, means controlled at a calling station for operating said connector to establish a connection with a called station, a first switch for connecting a calling station' with said connector, a second switch for connecting the operators position with any one of said stations, a transfer key at the operators position, means responsive to the actuation of said key for disconnecting the outside line from the operators position and for holding it, a connection from the first switch to said operators position, means also responsive to the operation of said key for actuating the rst switch to select the connection to said position, a talking circuit established thereupon with a station through the last-mena key 'at each station,

10. In atele'phone system, a private ing said connector `to tioned connection, a key at each station, means responsive to the actuation of Ithe key at a station connected with the operators position to actuate the'- second'switch for connecting the last-mentioned station with the operators position and therethrough with the outside line.

branch exchange, a plurality of stations connected therewith, an `outside line terminating at said exchange, a connector switch at said exchange, means controlledat a calling station for .operat- `connect with any one of said stations, a first and a second finder switch,

leach havngla bank of terminals and wipers cooperating therewith, a

connection from the wipers of the iirst finder switch to the connector, multiple connections from the terminals o all said switches-to the stations, a connection from. the terminal "bank of the first under switch Vto the outside line, means responsive to the initiation of a call at a stationto `operate the firstnder to connect thecalling station with said connector, means responsive to the operation of said key when the first nder engages the terminals of the associated station to operate the second finder to connect said station with the outside line, and means responsive to the operation of said key when the outside line is connected with the associated station through the second finder switch for operating .the rst nder switch to select the terminals in which the connection to the-outside line terminates, and means operative thereupon for establishing a connec- .tion from said station over the second nder to the connector.

11. In a telephone system, a private branch exchange, a plurality of stations connected therewith, a connector for establishing a connection with any one of said stations, a first finder for connecting calling stations with said connector, said connector having a set of terminals connected to said stations and a set of cooperating wipers, an outside line terminating at said exchange, one of the sets of terminals in said connector being connected with said outside line, a second nder switch connected with said outside line, terminals for said second iinder switch multipled to said stations, means operable upon the initiation of a call on one of said stations for actuating the first finder to connect the calling station with the connector, and means operable upon the selection of said outside line by the connector for operating the second finder to connect the outside line with the calling station, and means operative thereupon for releasing the first finder and connector switches.

12. In a telephone system, a private branch exchange, a plurality of stations connected therewith, a connector switch, means controlled by a calling station for operating said connector to select any one of said stations, a rst finder operable upon the initiation of a call to connect the calling station with the connector, an operators position, an outside lien terminating thereat, a second finder for connecting a calling station with said position, a first listening key at the operators position, means responsive to the actuation of said key for connecting said position with the calling station over the second finder, a second listening key at the position, means responsive to the actuation of the second key for connecting the position with interconnected calling and called stations through the operated first finder and connector switches, and means operable when the sound key is actuated for send- 23 ing 'a distinctive signal to the interconnected stations.

13. In a private branch telephone exchange system, a plurality of substations, a plurality of local junction circuits, a plurality of call circuits, means including a connector numerically operated by the calling station for establishing a connection between the calling and called substations over a junction circuit and a call circuit, means operative upon the establishment of the connection for releasing the call circuit and the connector employed therein, means for establishing a talking connection between the calling and called stations over the junction circuit used in the connection, and means independent of the connector for supplying current to the talking connection.

14. The system according to claim 13, and means controlled by a substation for operating a connector to transfer a call from one station to another through the junction circuit employed in the connection and a call circuit.

15. In a private branch exchange, a plurality 24 of substations, a plurality of junction circuits, means operative upon the initiation of a call for seizing an idle junction circuit, means for establishing a connection between the calling and called stations over the seized junction circuit, means for preventing the seizure of a busy junction circuit by a calling station, a plurality 0f outside trunks leading to the exchange, means for seizing an idle one of said trunks for the establishment of an outside connection and for preventing the seizure of busy trunks, and means for preventing the seizure of an idle junction circuit when all said trunks are busy.

FERNAND PIERRE GOHOREL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,214,914 Voss Sept. 17, 1940 2,070,874 Voss Feb. 16, 1937 

